More particularly this invention relates to certain improvements in surveys of the type disclosed and claimed in prior U.S. Pat. No. 4,515,458 to William H. Seager, entitled "Closely Spaced Pipe-to-Soil Electrical Survey, Method and Apparatus", and U.S. Pat. No. 4,228,399, to Frank E. Rizzo et al, entitled "Offshore Pipeline Electrical Survey Method and Apparatus". Such prior patents are incorporated herein by reference.
The surveys of such prior patents are used throughout the world and are conducted by Harco Corporation of Medina, Ohio under the service mark CPL, which is an acronym for computerized potential log. Such surveys utilize a relatively fine lightweight wire which is economically disposable. While it is such wire which makes the surveys ecnomically advantageous, such wire can also cause problems due primarily to its very lightweight nature. Such problems are caused by line breakage. Offshore, a tuna trawler or other boat may cross the survey causing line breakage. Breakage can also be caused even by fish or rather easily bad weather. Offshore, when a wire break occurs it is essentially impossible to locate the break and the survey must generally be started over. This can add hours or even days to a survey project which can be very costly if a substantial crew and expensive equipment is involved.
Onshore, breakage can be caused by children playing along the right-of-way, cows, tractors or other vehicles, particularly if the survey crosses a highway. With such breakage the only prior solution was to find the break and repair it or start over. Both expedients cause obvious economic problems particularly if there is a substantial gap caused by the break. Moreover, the wire may break again before the survey can be restarted.
There are also situations during a survey when the surveyor knows that a break is about to occur. Therefore, the surveyor may wish to initiate a disconnect. A typical example offshore would be during rough weather or when a vessel can be sighted about to cross the path of the survey. If onshore, such situations may exist as the result of obstacles such as highways, railroads, or rivers. It may also occur where the surveyor may wish to initiate the survey the next day from a given location or reference point such as the edge of a field. Accordingly, it would be highly advantageous to be able to conduct surveys as shown in the above patents which can be continued in the event of wire line breakage when accidental or intentional.